Evening star. [volume] (Washington, D.C.) 1854-1972, 1887-07-30
CITY AND DISTRICT.
COLD WAVES.
1SW they are Made. and How they
Can be ForetOld ON the Weather

- The Editor of The EVENING STAR:
The term ''cOld wave must necessarily be
relative expression for II cannot be spoken OF In
positive manner. To understand the conditions
which produce the 'cold wave" and, indeed, TO
understand the science OF meteOrology at all, we
must refer TO that wonderful modern acquisition,
0o weather map. BY the study OF this map we
nay readily understand the nature and cause OF
the 'cold wave" and why the expression must be
Q relative one.
The map shows the two grand factors, "high"
and "iow,r meaning high and low barometer. AS
often stated, "hgh' IS cOld-day factor and posi-
tive In degree in proportion TO its extent and IN
tenstty. Thirty and seven-tenths IS high for the
United States, though occasionally II VIII go as
high az 30.9 and sometimes even as high as 81
inches. Thirty and Seven-tenthS Is even more
than average. The lines on the map, showing
the sections OF equal or nearly equal pressure, are
termed '.qrddlents.' When these ''grddtents, are
cloae together the conditions are positive; when
Tar apart they are negative. ON the same princi-
pie the civil engineer represents the varied lopo-
Graphy OF the country. When the gradients are
near together they represent sudden or positive
changes In the altitude OF the country; when they
far apart they show very gradual rises ana oe-
pfessions. IL the engineer desired 10 represent q
high plateau Of equal altitude ne aIaIYe
circular line against which he would put Certain
0gureS which would represent the leisht vi lnat
plateau. ON the weather map the pressure or the
Atmosphere Is represented in a similar manner
Every day the heavy lines on the map snow the
sections OF country that are under an equal Daro-
Il marked "high," while The center Oh lhe iowest
pressure Is marked slow" "High" Is the coid dry
factOr The movement or the atmosphere Is, on
general lines, from the "high" toward the low
Il could not at all places, be direct toward the
siow" for the simple reason that the winds from
the different points OF the compass as they near
this center react upon each otner ana more or less
change their direction The movement OF the ar
being from the "hgh 1t has little opportunity 70
become heated. north slow hea.S because OF
the movement TO the south OF IL OF the warm
S0utherly winds while south slows is cold be-
cause of the cold north winds moving toward It,
As the general movement IS from the west toward
tho east, when a "high" Is discovered In the west
We know that In due time 1t means cooler weather
for the territory over which IL Will pass III these
s.highS" would move along on regular and fixed
highways, and would move at some regular speed,
ls would only be question OF simple arithmetic
when IL would be cooler at certain point,
but they do not The movement or the atmoS-
phere Is most irregular and uncertain as 10 speed
and direction; ami IN addition 10 this IL Is equally
uncertain as 10 intensity of pressure. The nigh
70 the "cold wave" proper, though sometimes the
change 70 cooler temperature generated Dy q sOutn
low Il spoken OF ''coOl wave" This Is hardly
proper for the reason that IL Is not akin 10 cool
wave" from "hiSh," for as IL WORKS us way
northward IL becomes a warmer and warmer
ssWave," and II IL reach q far north line IL Will
cause Q very warm "wave;" so the term ''cOld
wave" had better be confined 10 the ''hish-" The
more intense and extensive the ''hlgh' the more
positive the 'cOld wave produced by IL; Dut III, as
II advances eastward 1t takes very Tar north
une IL may pass US with little or no effect; and
likewise Its effect may be greatly neutraliZed, or
reduced 10 q minimum II IL becomes reduced In
intensity. sometimes IL will be reduced 10 thirty
andone-tenth, or even 70 thirty; In that Case Its
wave" depends upon ''hlgh;" the more extensive
the inner Lines or plateau OF "high" the more In
tense the pressure and the more central IL strikes
certain locality the more positive will the 'cold
no positive "highs," hence the continued oppres-
s1ve heat i. +. n.